It was discovered that PostgreSQL versions before 10.5, 9.6.10, 9.5.14, 9.4.19, and 9.3.24 failed to properly check authorization on certain statements involved with "INSERT ... ON CONFLICT DO UPDATE". An attacker with "CREATE TABLE" privileges could exploit this to read arbitrary bytes server memory. If the attacker also had certain "INSERT" and limited "UPDATE" privileges to a particular table, they could exploit this to update other columns in the same table.
https://www.postgresql.org/about/news/1878/
https://www.debian.org/security/2018/dsa-4269
https://usn.ubuntu.com/3744-1/
https://security.gentoo.org/glsa/201810-08
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10925
https://access.redhat.com/errata/RHSA-2018:3816
https://access.redhat.com/errata/RHSA-2018:2566
https://access.redhat.com/errata/RHSA-2018:2565
https://access.redhat.com/errata/RHSA-2018:2511
http://www.securitytracker.com/id/1041446
http://www.securityfocus.com/bid/105052
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00043.html